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3:3 pull-down for real?

by berock / December 15, 2004 2:29 AM PST

I'm familiar with 2:3 pull-down for video to compensate for conversion of 24 frames per second (fps) on film to 30 fps on TV. Lately, I see some plasma TVs promoting "3:3 pull-down". (Mathematically 3:3 is the same as 1:1.) What exactly is 3:3 pull-down? (Just marketing hype?) If 3:3 pull-down is for real on these plasma TVs, to actually achieve any benefit, does the input (DVD, DVR, cable, satellite, etc.) as well have to be at this 3:3 pull-down compatability?

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yes it is real
by kbart63 / January 25, 2005 8:54 AM PST

Movies run at 24 fps, while television is a 30 fps medium (60 fields).

When you go to a theatre they actually show the same frame 2 times (it may actually be 3 times, but for this explanation we will use the number 2; you can google to find out what the correct answer is) It is actually doing something like blocking the frame so that the projector blinked 48 times, it showed 24 frames twice in 1 second.

This is an optical trick that makes movies look smooth like. Our eyes cannot tell the same frame is shown twice.

When you try to get 24 frames played correctly on a monitor that only displays 30 frames a second, but refreshes at 60 you need to use the 3:2 method to have it work properly and look movie like. You still have problems where pans and other camera shots will not look correct on a tv becasue of how you are displaying the frames. (google this to get a better explanation about 3:2 pulldown)

Now what if the monitor can refresh 72 times per second. 24 divides by 72 equally and now you can display each frame 3 times and you avoid the problems of 3:2 pulldown and get the full movie experience.

This is a simplification and 3:3 may have judder and other problems if not properly implemented (ie, your dvd player is doing 3:2 pulldown, but your monitor is running at 72 hertz) I have not see this myself live, but I have been noticing some plasmas support refershing 72 times a second.

Hope that was clear. It is not a gimmick and is a step in the right direction. You should check for more information.

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yes it is real, but
by jcrobso / February 1, 2005 12:07 AM PST
In reply to: yes it is real

Well lets go back and talk about the 24fps movie and how you get it to 30fps video. It is done by scanning every 4th frame twice. So the movie frames would be scaned 1,2,3,4,4,5,6,7,8,8,9,10,11,12,12, etc. This will give you 30 tv frames by the time you get to 24 movie frames. and requires a special projector.
In the movie theatre what you are talking about is the flash or flicker rate that is used to project the movie in a theater. Ever heard movies refered to as the the flicks? To stop the flickering of movies EACH frame was double or tripple flashed on the screen by a rotating shutter in the projector, this flashing is what fools your eyes into "seeing" motion without flickering.
When you talk about video there is a difference between
regular TV and watching DVDs on a PC.
One TV frame is made up 2 fields of 262.5 interlaced scanlines so when both fields have been scaned the result is one frame of 525 scan lines. This is the NTSC
standard on a regular TV since 1946 or so.
DVDs played on a standard TV will follow the above format.
DVDs on a PC will be at full DVD resulion will be shown in a progressive scan format and show the full frame and not the overscaned frame as on a TV. HDTV monitor using component connections will also do this.

What you are talking about in computer video is similar but not the same. Many people complane about filcker in the computer monitors when the the virtical refersh rate is set to 60hz ( the MS default ) and the have florescent lighting in the office, I usualy "fix" this by setting the rate to 72hz. A higher refersh rate makes the picture look better, just as flashing the image on the screen 3 times does in the movies. John

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Thanks for the clarification!
by berock / March 20, 2005 9:17 AM PST
In reply to: yes it is real, but

I appreciate your explanation!

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I appreciate your explanation
by berock / March 20, 2005 9:20 AM PST
In reply to: yes it is real

Thanks for education! I wish the HDTV magazine and the manufacturers themselves provided as thorough an explanation.

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